Emission control devices, such as diesel particulate filters (DPF), may reduce the amount of soot emissions from a diesel engine by trapping soot particles. Such devices may be regenerated during operation of an engine, such as a turbocharged engine, to decrease the amount of trapped particulate matter. Regeneration is typically achieved by raising the temperature of the DPF to a predetermined level, and ensuring that the exhaust gas entering the DPF is of a certain composition.
One approach for controlling filter regeneration terminates a regeneration event when the amount of particulate remaining in the filter falls below a threshold, or alternatively when a percentage of particulate filter storage (relative to a total capacity) falls below a percentage threshold.
However, the inventors herein have recognized issues with such an approach. For example, under some operating conditions, the amount of time it takes to remove particulates at lower storage levels can be considerable. Thus, regeneration duration may be extended significantly during such operating conditions. Extending regeneration under such conditions to remove only small amounts of particulate can be inefficient, particularly in terms of fuel economy due to the additional fuel spent maintaining elevated regeneration temperatures.
In one example approach, the above issue can be at least partially addressed by a method for controlling regeneration of a diesel particulate filter in an engine exhaust, comprising: terminating regeneration based on a particulate burning rate. For example, during some conditions, even at lower particulate storage levels, a sufficiently high soot burning rate may occur. Under such conditions, the regeneration may be terminated at a lower soot storage level, thus allowing longer storage during a subsequent storage operation of the filter. However, under other conditions, during lower particulate storage levels, the soot burning rate may be sufficiently low that the regeneration is terminated at a higher soot storage level. Thus, even though a subsequent storage operation may be reduced, this is a lower penalty than continuing regeneration.
In one particular example, regeneration termination may be based on a variable threshold of stored particulate, where the threshold of stored particulate depends on a current soot burn rate. The regeneration termination may be further based on vehicle speed. In such an approach, the duration of a regeneration event may be extended to further reduce the amount of soot stored at low levels depending on whether the soot burning rate is above a threshold. As such, the intervals between regeneration events may be extended under selected conditions where such an extension results in meaningful additional soot removal. In this way, reduced fuel consumption may be achieved by not extending the duration at low soot storage levels when the soot burning rate is below the threshold. Further, it may be possible to achieve reduction in tailpipe emissions due to reduction in emissions penalties from regeneration and improvement in fuel in oil dilution which may potentially extend oil change intervals.
It should be understood that the background and summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.